White light emitting diode and method of manufacturing the same

ABSTRACT

Provided is a white LED including a reflector cup; an LED chip mounted on the bottom surface of the reflector cup; transparent resin surrounding the LED chip; a phosphor layer formed on the transparent resin; and a light transmitting layer that is inserted into the surface of the phosphor layer so as to form an embossing pattern on the surface, the light transmitting layer transmitting light, incident from the phosphor layer, in the upward direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.12/068,998, filed on Feb. 14, 2008, which claims the benefit of KoreanPatent Application No. 10-2007-0132469 filed with the Korea IntellectualProperty Office on Dec. 17, 2007, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a white light emitting diode (LED) anda method of manufacturing the same.

2. Description of the Related Art

An LED is referred to as a device which generates minority carriers(electrons or holes) injected by using the p-n junction structure ofsemiconductor and emits light by recombining the minority carriers. Asfor the LED, a red LED using GaAsP or the like, a green LED using GaP orthe like, and a blue LED using InGaN/AlGaN double hetero structure areprovided.

The LED has low power consumption and a long lifespan. Further, the LEDcan be installed in a narrow space, and has high resistance tovibration. The LED is used as a display device and a backlight unit.Recently, researches are being actively conducted to apply the LED as ageneral lighting.

Recently, white LEDs as well as red, blue, or green LEDs are launched onthe market.

Since the white LEDs can be applied to various fields, it is expectedthat demand for the white LEDs is rapidly increasing.

A technique for implementing white light in the LED can be roughlydivided into two techniques.

In the first technique, red, green, and blue LED chips are installedadjacent to each other, and lights emitted from the respective LED chipsare mixed to implement white light. However, since the respective LEDchips have different thermal or time characteristics, the color tones ofthe LED chips are changed depending on the surrounding environment. Inparticular, color spots may occur, which makes it difficult to implementa uniform mixed color.

In the second technique, phosphor is disposed in an LED chip. Some ofprimarily-emitted light from the LED chip and secondarily-emitted light,of which the wavelength is converted by the phosphor, are mixed toimplement white light. That is, phosphor which is excited by ultraviolet(UV) light so as to emit visible light from blue to red is coated on theLED chip which emits UV light, thereby obtaining white light.Alternately, on an LED chip which emits blue light, phosphor isdistributed, the phosphor emitting yellow-green or yellow light by usingthe blue light as an excitation source. Then, white light can beobtained by the blue light emitted from the LED chip and theyellow-green or yellow light emitted from the phosphor.

Between them, the second technique is generally used. In particular, thetechnique for implementing white light by using the blue LED chip andthe yellow-green or yellow phosphor is most frequently used.

FIG. 1 is a cross-sectional view of a conventional lamp-type white LEDwhich uses a white LED chip and yellow light emitting phosphor so as toimplement white light.

As shown in FIG. 1, the lamp-type white LED 10 includes a mount lead 11,an inner lead 12, and an LED chip 14 installed in a reflector cup 20formed in the upper portion of the mount lead 11. Further, n- andp-electrodes of the LED chip 14 are electrically connected to the mountlead 11 and the inner lead 12, respectively, through a wire 15.

The LED chip 14 is covered by a phosphor layer 150 which is obtained bymixing phosphor materials with transparent resin. The above-describedcomponents are surrounded by an encapsulation member 17.

The reflector cup 20 is coated with silver (Ag) and aluminum (Al) toreliably reflect visible light.

FIGS. 2A and 2B are diagrams simply showing a case where phosphormaterials are disposed in the reflector cup.

As shown in the drawings, the LED chip 14 is mounted on the bottomsurface of the reflector cup 20, and the transparent resin 16 is filledin the reflector cup 20. Further, the phosphor materials 19 aredistributed in the transparent resin 16.

As shown in FIG. 2A, the phosphor materials 19 may be uniformlydistributed in the transparent resin 16. Alternately, as shown in FIG.2B, the phosphor materials 19 may be concentrated on the surface of theLED chip 14.

When a current is applied, the LED 10 including the phosphor materials19 mixed with the transparent resin 16 implements white light bycombining blue light emitted from the LED chip 14 and yellow lightemitted from the phosphor materials 16 using some of the blue light asan excitation source.

However, some of light emitted from the phosphor materials 19, which areexcited by the light emitted from the LED chip 14, collides with thesurface of the LED chip 14 so as to be re-absorbed. Therefore, lightemission efficiency decreases.

As shown in FIG. 2B, when the phosphor materials 19 are concentrated onthe surface of the LED chip 14, it is highly likely that the lightemitted from the phosphor materials 19 collides with the surface of theLED chip 14, compared with the case where the phosphor materials 19 areuniformly distributed in the transparent resin 16. Therefore, the lightemission characteristic is degraded.

SUMMARY OF THE INVENTION

An advantage of the present invention is that it provides a white LED inwhich only transparent resin is filled around an LED chip Mounted on thebottom surface of a reflector cup, a phosphor layer is formed on thetransparent resin, and spherical particles are inserted into the surfaceof the phosphor layer such that an embossing pattern is provided on thesurface. In the white LED, light directed from the phosphor layer towardthe LED chip is transmitted upward, thereby enhancing light extractionefficiency.

Another advantage of the invention is that is provides a method ofmanufacturing a white LED.

Additional aspects and advantages of the present general inventiveconcept will be set forth in part in the description which follows and,in part, will be obvious from the description, or may be learned bypractice of the general inventive concept.

According to an aspect of the invention, a white LED comprises areflector cup; an LED chip mounted on the bottom surface of thereflector cup; transparent resin surrounding the LED chip; a phosphorlayer formed on the transparent resin; and a light transmitting layerthat is inserted into the surface of the phosphor layer so as to form anembossing pattern on the surface, the light transmitting layertransmitting light, incident from the phosphor layer, in the upwarddirection.

The transparent resin may be selected from the group consisting ofpolymethyl methacrylate (PMMA), polysterene, polyurethane,benzoguanamine resin, epoxy, and silicon resin.

The phosphor layer may be formed by mixing transparent resin andphosphor materials. In this case, the transparent resin may be selectedfrom the group consisting of PMMA, polysterene, polyurethane,benzoguanamine resin, epoxy, and silicon resin.

Preferably, the light transmitting layer has the same refractive indexas that of the transparent resin. In this case, the transparent resinmay be selected from the group consisting of PMMA, polysterene,polyurethane, benzoguanamine resin, epoxy, and silicon resin.

The light transmitting layer may be formed of a plurality of sphericalparticles, and the diameters of the spherical particles range from 5 to100 μm.

The LED chip may include at least one or more LEDs which generate blue,red, green, and ultraviolet (UV) wavelengths. Further, the phosphorlayer may include at least one or more phosphor materials which converta wavelength into any one of yellow, red, and green.

According to another aspect of the invention, a white LED comprises areflector cup that is inclined upward; an LED chip that is mounted onthe bottom surface of the reflector cup; a molding compound that isfilled in the reflector cup so as to surround the LED chip; a phosphorlayer that is formed on the molding compound; and a light transmittinglayer that is formed by inserting a plurality of spherical particlesinto the surface of the phosphor layer such that an embossing pattern isformed on the surface. A ratio of the radius of the spherical particlesto the height of the embossing pattern from the surface of the phosphorlayer ranges from 0.6 to 1.

Preferably, the diameters of the spherical particles composing the lighttransmitting layer range from 5 to 100 μm, and the light transmittinglayer has the same refractive index as that of the molding compound.

The light transmitting layer may be formed of any one selected from thegroup consisting of PMMA, polysterene, polyurethane, benzoguanamineresin, epoxy, and silicon resin.

According to a further aspect of the invention, a method ofmanufacturing a white LED comprises the steps of: preparing a reflectorcup; mounting an LED chip on the bottom surface of the reflector cup;forming a molding compound in the reflector cup such that the LED chipis surrounded by the molding compound; forming a phosphor layer on themolding compound; and forming a light transmitting layer by inserting aplurality of spherical particles into the phosphor layer such that anembossing pattern is formed on the surface of the phosphor layer.

The molding compound may be formed of any one selected from the groupconsisting of PMMA, polysterene, polyurethane, benzoguanamine resin,epoxy, and silicon resin.

The forming of the phosphor layer may include the steps of: mixingtransparent resin with phosphor materials, and then dispensing thetransparent resin and the phosphor materials on the molding compound;and semi-curing the transparent resin and the phosphor materialsdispensed on the molding compound.

The forming of the light transmitting layer may include the steps of:semi-curing the phosphor layer; preparing a container in whichspherical-particle powder is stored; preparing a support bar having asheet for bonding the spherical-particle powder, the sheet beingattached to the lower surface of the support bar; putting the sheet intothe container such that the spherical-particle powder is bonded to thesurface of the sheet; placing the sheet having the spherical-particlepowder bonded thereon onto the semi-cured phosphor layer, and applyingpressure to insert the spherical particles into the phosphor layer; andseparating the support bar from the phosphor layer.

The method may further include the step of completely curing thephosphor layer after the spherical particles are inserted into thephosphor layer. Preferably, the diameters of the spherical particlesrange from 5 to 100 μm.

Preferably, a ratio of the radius of the spherical particles to theheight of the embossing pattern from the surface of the phosphor layerranges from 0.6 to 1.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present generalinventive concept will become apparent and more readily appreciated fromthe following description of the embodiments, taken in conjunction withthe accompanying drawings of which:

FIG. 1 is a cross-sectional view of a conventional lamp-type white LED;

FIGS. 2A and 2B are diagrams simply showing a case where phosphormaterials are distributed in a reflector cup of the conventionallamp-type white LED;

FIG. 3 is a cross-sectional view of a white LED according to theinvention;

FIGS. 4 and 5 are conceptual diagrams for explaining the Snell's lawwhich is applied to the invention;

FIG. 6 is a diagram showing light extraction of the white LED accordingto the invention;

FIG. 7 is a graph showing light transmittance depending on wavelengthsin a case where the size of spherical particles is set to 10 μm;

FIG. 8 is a graph showing light transmittance depending on wavelengthsin a case where the size of spherical particles is set to 30 μm;

FIG. 9 is a graph showing light transmittance depending on a ratio ofradius and height of particles;

FIGS. 10A to 10C are process diagrams showing a method of manufacturinga white LED according to the invention; and

FIGS. 11A to 11C are process diagrams showing a process of forming alight transmitting layer according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentgeneral inventive concept, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to likeelements throughout. The embodiments are described below in order toexplain the present general inventive concept by referring to thefigures.

Hereinafter, a white LED and a method of manufacturing the sameaccording to the present invention will be described in detail withreference to the accompanying drawings.

FIG. 3 is a cross-sectional view of a white LED according to theinvention, showing a state where an LED chip is mounted on a reflectorcup.

As shown in FIG. 3, the white LED 100 according to the inventionincludes a reflector cup 120, an LED chip 110 mounted on the bottomsurface of the reflector cup 120, a molding compound 130 surrounding theLED chip 110, a phosphor layer 150 formed on the molding compound 130,and a light transmitting layer 160 formed on the phosphor layer 150.

The reflector cup 120 has a structure that is inclined upward. The innerwall of the reflector cup 120 is coated with a reflective material forreflecting light which is emitted from the LED chip 110 and is thendirected to a side portion or lower portion of the reflector cup 120.

As for the reflective material, silver (Ag), aluminum (Al) and so on maybe used, which have an excellent reflective property with respect tovisible light.

The LED chip 110 may include one or more LEDs which generate blue, red,green and ultraviolet (UV) wavelengths. For example, the LED chip 110may include only a blue LED or both blue and red LEDs.

However, the present invention is not limited to such examples. If blue,red, green and ultraviolet (UV) wavelengths can be generated, an LED canbe independently used or another combination of LEDs can be used.

The molding compound 130, which is filled in the reflector cup 120 so asto surround the LED chip 110, is composed of transparent resin which cantransmit visible light generated from the LED chip 110. For example, themolding compound 130 may be formed of any one of polymethyl methacrylate(PMMA), polysterene, polyurethane, benzoguanamine resin, epoxy, andsilicon resin.

The phosphor layer 150 is formed by mixing phosphor materials 153 withtransparent resin 151. A material forming the transparent resin 151 isnot specifically limited, if the material can transmit light generatedfrom the LED chip 110 and light emitted from the phosphor materials 153and can stably disperse the phosphor materials 153. For example, thetransparent resin 151 may be formed of any one of PMMA, polysterene,polyurethane, benzoguanamine resin, epoxy, and silicon resin, like themolding compound 130.

The phosphor materials 153 may be formed of phosphor which converts awavelength into any one of yellow, red, and green. The phosphormaterials 153 of the phosphor layer 150 are determined depending on theemission wavelength of the LED chip 110. That is, phosphor materials areused, which can convert light emitted from the LED chip 110 so as toimplement white light. For example, when the LED chip 110 generates bluelight, the phosphor layer 150 is formed of a phosphor material which canemit yellow light.

As such, when the blue LED and the yellow light emitting phosphor areused, blue light emitted from the LED chip 110 and yellow light emittedfrom the phosphor materials using some of the blue light as anexcitation source are combined at the time of the application ofcurrent, thereby implementing white light.

The light transmitting layer 160 is formed by inserting a plurality ofspherical particles 160 a into the surface of the phosphor layer 150,the spherical particles 160 a forming an embossing pattern on thesurface.

Further, the spherical particles 160 a forming the light transmittinglayer 160 have the same refractive index as the molding compound 130 andmay be formed of any one of PMMA, polysterene, polyurethane,benzoguanamine resin, epoxy, and silicon resin.

The light emitting layer 160 forming the spherical embossing pattern onthe surface of the phosphor layer 150 transmits light generated from theLED chip 110 and refracts phosphorescence of the phosphor layer 150,which is directed downward, to the upper direction such that thephosphorescence is transmitted. Therefore, light extraction efficiencyis enhanced.

Refraction is referred to as a phenomenon in which when light isincident on a different transparent medium, the light does not enter themedium straightly, but is bent and then propagates straightly. Arefractive index indicates how much light is bent when the light entersa medium. A refractive index determined in a vacuum state is referred toas an absolute refractive index. The absolute refractive index isusually called a refractive index.

For example, when the speed of light in the vacuum is represented by Cand the speed of light in a medium is represented by V, a refractiveindex can be expressed by Equation 1.Refractive Index n=C/V  [Equation 1]

Therefore, the refractive index in the vacuum state is 1. Since thespeed (V) of light in a medium is smaller than the speed (C) of light inthe vacuum, a refractive index is always larger than 1.

Meanwhile, a predetermined rule for refraction in a certain medium isestablished between an incident angle and a refraction angle. This isreferred to as the Snell's law.

When a medium has a large refractive index, it indicates that the mediumis an optically dense medium. Further, the speed of light in the mediumbecomes low. On the contrary, when a medium has a small refractiveindex, it indicates that the medium is an optically thin medium. Suchterms are relatively used at all times.

FIGS. 4 and 5 are conceptual diagrams for explaining the Snell's lawwhich is applied to the invention. FIG. 4 shows a case where aninterface between two media is flat, and FIG. 5 shows a case where aninterface between two media is formed in a hemispherical shape.

As shown in FIG. 4, when light is incident from an optically densemedium n2 to an optically thin medium n1, the speed of the light in theoptically thin medium n1 becomes so high that the propagation directionof the light is bent toward a direction away from a vertical line.

Meanwhile, when light is incident at more than a predetermined angle,the light is not refracted at a flat interface, but is reflected. Such aphenomenon is referred to as total reflection (which is represented by adashed line in FIG. 4). An angle at which the total reflection occurs isreferred to as a critical angle θ_(c). As a difference in refractiveindex between two media increases, the critical angle θ_(c) decreases.Then, the total reflection of incident light frequently occurs.

Therefore, to reduce the total reflection, the critical angle at theinterface should be increased. In the invention, the interface betweentwo different media is formed in a hemispherical shape so as to increasethe critical angle.

That is, as shown in FIG. 5, when a hemispherical pattern 160′ isprovided at the interface between two media, most of light incident onthe optically thin medium n1 from the optically dense medium n2 can betransmitted without total reflection.

The present invention takes advantage of such an optical characteristic.The light transmitting layer 160 is formed by inserting the sphericalparticles 160 a into the surface of the phosphor layer 150 such that theembossing pattern is formed on the surface. Therefore, it is possible toprevent light, incident from the phosphor layer 150, from being totallyreflected at the interface.

More specifically, as shown in FIG. 6, when blue light (1) is emittedfrom the LED chip (not shown) positioned under the phosphor layer 150,the blue light (1) collides with the phosphor materials 153 so as toexcite the phosphor materials 153 distributed in the phosphor layer 150and are then discharged upward (1 a) or directed downward (1 b). At thistime, most of the blue light excites the phosphor material 153 and arethen discharged upward. Further, most of the light incident in thedownward direction is reflected by the reflector cup so as to againexcite the phosphor materials 153 and is then discharged upward.

The phosphor materials 153 excited by the blue light (1) generate yellowlight (2 a and 2 b). In this case, most of the yellow light (2 a and 2b) is discharged upward with the blue light (1 a) without being totallyreflected, thereby implementing white light.

As such, most of light is transmitted to the outside by the lighttransmitting layer 160 formed of the spherical particles 160 a, withoutbeing totally reflected. That is, when the light transmitting layer 160is not provided on the phosphor layer 150, light incident at a largerangle than the critical angle is totally reflected at the flatinterface. However, as the critical angle is increased to almost 90degrees by the light transmitting layer 160, most of light incident fromthe phosphor layer 150 to the outside is transmitted without totalreflection.

Meanwhile, the diameter of the spherical particles 160 a can set in therange of 5 to 100 μm, and the size of the spherical particles 160 a hasan effect upon light transmittance depending on wavelengths.

FIG. 7 is a graph showing light transmittance depending on wavelengthsin a case where the size of the spherical particles is set to 10 μm, andFIG. 8 is a graph showing light transmittance depending on wavelengthsin a case where the size of the spherical particles is set to 30 μm. InFIGS. 7 and 8, ‘A’ represents light transmittance of a structure with nolight transmitting layer, and ‘B’ represents light transmittance of astructure with the light transmitting layer.

As shown in FIG. 7 where the light transmitting layer is formed ofspherical particles with a diameter of 10 μm, when the wavelength ofincident light is smaller than 0.45 μm, the light transmittance rapidlydecreases. However, when the wavelength is larger than 0.55 μm, lightextraction efficiency is enhanced by about 5%, compared with when thelight transmission layer is not provided. In this case, the lighttransmittance is about 95%.

Further, as shown in FIG. 8, when the diameter of the sphericalparticles is set to 30 μm, it can be found that the light transmittanceincreases when the wavelength of incident light is larger than 0.425 μm.

As described above, the size of the spherical particles 160 a has aneffect upon the light transmittance depending on wavelengths.

Therefore, the size of the spherical particles 160 a can be adjusted invarious manners, depending on the wavelength of light transmitted to theoutside.

Meanwhile, the light transmittance is determined by a ratio (r/h) of theradius (r) of the spherical particle 160 a to the height (h) of thespherical particle 160 a from the surface of the phosphor layer 160,that is, the height of the embossing pattern formed on the surface ofthe phosphor layer by the spherical particles.

Here, the light transmittance means a quantity of light transmitted tothe outside through the phosphor layer, and may be considered as lightextraction efficiency.

FIG. 9 is a graph showing light extraction efficiency depending on theratio (h/r) of the radius (r) of the spherical particle to the height(h) of the spherical particle from the surface of the phosphor layer,the light extraction efficiency being measured as the intensity oflight. Here, FIG. 9 shows the intensity of light depending on a changein the height of the spherical particle from the surface of the phosphorlayer, because the radius (r) of the spherical particle is constant.

As shown in FIG. 9, it can be found that as the height (h) increases,the intensity of light, that is, the light extraction efficiencyincreases. However, the light extraction efficiency does notcontinuously increase in accordance with the height (h) of the particle.When the ratio (h/r) of the height and the radius is 0.6, the lightextraction efficiency is maximized. When the ratio exceeds 0.6, thelight extraction efficiency slightly decreases.

Therefore, the light extraction efficiency can be adjusted by the radiusof the spherical particle and the height of the spherical particle fromthe surface of the phosphor layer, that is, the height of the embossingpattern formed on the surface of the phosphor layer.

As described above, the white LED 100 has the light transmission layer160 formed by implanting the spherical particles 160 a into the surfaceof the phosphor layer 150 such that the embossing pattern is provided onthe surface. Then, the critical angle at which the total reflectionoccurs is increased at the maximum such that light lost on the surfaceof the conventional phosphor layer by the total reflection istransmitted to the outside. Therefore, it is possible to increase thelight extraction efficiency.

With the light transmitting layer 160 provided on the phosphor layer150, it is possible to increase the light extraction efficiency by 5 to30%, compared with when the light transmitting layer is not provided.

Meanwhile, the white LED 100 according to the invention is formed by thefollowing process. First, the LED chip 110 is mounted on the bottomsurface of the reflector cup 120. After the transparent resin 151 isfilled by a jetting method such as dispensing or the like so as tosurround the LED chip 110, the transparent resin 151 is cured to formthe molding compound 130. Then, the phosphor layer 150 and the lighttransmitting layer 160 are consecutively formed on the molding compound130.

FIGS. 10A to 10C are process diagrams briefly showing a method ofmanufacturing a white LED according to the invention.

First, as shown in FIG. 10A, a reflector cup 120 is prepared, and an LEDchip 110 is mounted on the reflector cup 120. At this time, the innersurface of the reflector cup 120 may be coated with a reflectivematerial such as silver (Ag) or aluminum (Al) for reflecting lightincident on the reflector cup 120 from the LED chip 110 such that thelight is directed upward.

Continuously, transparent resin is filled by a jetting method such asdispensing or the like so as to surround the LED chip 110 and is thencured to form a molding compound 130.

The transparent resin 151 may be formed of any one of PMMA, polysterene,polyurethane, benzoguanamine resin, epoxy, and silicon resin.

As shown in FIG. 10B, resin obtained by mixing transparent resin withphosphor materials is coated on the molding compound 130 and is thensemi-cured. After that, spherical particles 160 a are inserted into thesurface of the semi-cured phosphor layer 150 a, thereby forming a lighttransmitting layer 160 on which an embossing pattern is formed.

The spherical particles 160 a are formed to have the same refractiveindex as the molding compound 130 and may be formed of any one of PMMA,polysterene, polyurethane, benzoguanamine resin, epoxy, and siliconresin.

The inserting of the spherical particles 160 a into the surface of thesemi-cured phosphor layer 150 a is performed as follows. A sheet forbonding the spherical particles is prepared, and is then pressed againstthe semi-cured phosphor layer 150 a to insert the spherical particles.

FIGS. 11A to 11C are diagrams showing the method for inserting thespherical particles 160 a. First, as shown in FIG. 11A, a container 180in which spherical-particle powder 170 is stored and a support bar 195having a sheet 190 which can bond the spherical-particle powder areprepared. At this time, the sheet 190 may be formed of cloth or sponge.

Then, as the sheet 190 is put into and taken out of the container 180,the spherical-particle powder 170 is bonded to the surface of the sheet190. At this time, the spherical-particle powder 170 may includespherical particles having a diameter of 5 to 100 μm.

Continuously, as shown in FIG. 11B, the sheet 190 to which thespherical-particle powder is bonded is contacted with the semi-curedphosphor layer 150 a, and predetermined pressure is applied to implantthe spherical particles 160 a into the surface of the phosphor layer150. At this time, since a depth at which the spherical particles 160 aare implanted into the surface of the phosphor layer 150 is determinedby the pressure applied to the sheet 190, the pressure should be appliedin such a manner that the spherical particles 160 a are not completelyburied into the phosphor layer 150.

Next, as shown in FIG. 11C, when the sheet 190 is separated from thephosphor layer 150 a, the spherical particles 160 a implanted into thesurface of the phosphor layer 150 a remain as they are.

This can be realized because since the phosphor layer 150 a issemi-cured, the bonding force of the phosphor layer caused by theviscosity of the transparent resin of the phosphor layer is larger thanthat of the sheet.

After the spherical particles 160 a are inserted into the semi-curedphosphor layer 150 a, the phosphor layer 150 is completely cured. Then,as shown in FIG. 10C, the white LED 100 is formed.

The white LED 100 obtained by the above-described method according tothe invention transmits all light, generated from the phosphor layer150, to the outside through the light transmitting layer 160 by usingthe light emitted from the LED chip 110 as an excitation source, therebyenhancing the light extraction efficiency.

The basic concept of the invention is that the spherical particles areinserted into the surface of the phosphor layer so as to form the lighttransmitting layer having an embossing pattern formed thereon. If thebasic concept is included regardless of a mounting method for LED, apackaging method and so on, all white LEDs belong to the invention.

According to the invention, as the spherical particles are inserted intothe phosphor layer such that the embossing pattern is formed on thesurface of the phosphor layer, the critical angle at which the totalreflection occurs is increased. Therefore, phosphorescence which isgenerated from the phosphor layer so as to be discharged downward istransmitted to the outside, thereby enhancing light extractionefficiency.

Although a few embodiments of the present general inventive concept havebeen shown and described, it will be appreciated by those skilled in theart that changes may be made in these embodiments without departing fromthe principles and spirit of the general inventive concept, the scope ofwhich is defined in the appended claims and their equivalents.

1. A method of manufacturing a white LED, comprising steps of: preparinga reflector cup; mounting an LED chip on a bottom surface of thereflector cup; forming a molding compound in the reflector cup such thatthe LED chip is surrounded by the molding compound; forming a phosphorlayer on the molding compound; and forming a light transmitting layer byinserting a plurality of spherical particles into the phosphor layersuch that an embossing pattern is formed on a surface of the phosphorlayer, wherein: the step of forming the light transmitting layerincludes the steps of: semi-curing the phosphor layer; preparing acontainer in which spherical-particle powder is stored; preparing asupport bar having a sheet for bonding the spherical-particle powder,the sheet being attached to a lower surface of the support bar; puttingthe sheet into the container such that the spherical-particle powder isbonded to a surface of the sheet; placing the sheet having thespherical-particle powder bonded thereon onto the semi-cured phosphorlayer, and applying pressure to insert the spherical particles into thephosphor layer; and separating the support bar from the phosphor layer.2. The method according to claim 1 further comprising the step of:completely curing the phosphor layer after the spherical particles areinserted into the phosphor layer.
 3. The method according to claim 1,wherein diameters of the spherical particles range from 5 to 100 um. 4.The method according to claim 1, wherein a ratio of the radius of thespherical particles to the height of the embossing pattern from thesurface of the phosphor layer ranges from 0.6 to 1.